Patrick Cantlay and Tony Finau shared the Genesis Open lead as the first round was suspended due to darkness, with Dustin Johnson making a poor start.
Cantlay and Finau fired five-under 66s at the Riviera Country Club to top the leaderboard on Thursday.
The American duo both made just a bogey apiece in strong openings at the PGA Tour event in California.
Tom Hoge, Dominic Bozzelli and Sam Saunders carded four-under 67s to be tied for third when play was suspended.
Only 12 players were unable to complete their first rounds, with Ben Silverman and Dou Zecheng (both even through 14) the best placed.
A host of big names made solid starts, but Johnson – the world number one and defending champion – was not among them.
The American, who has held the top ranking since winning the Genesis Open last year, carded a three-over 74 that included a triple bogey at the par-four fifth hole.
Rory McIlroy and Jordan Spieth opened with 71s, while Tiger Woods started with a one-over 72.
Woods had a mixed round that included five birdies, four bogeys and a double bogey.
Defending US PGA Championship winner Justin Thomas fired an opening-round 69 to be in a tie for 17th.
Phil Mickelson – a two-time champion and coming off back-to-back top-five finishes – is a shot further back.